Kurt writes: I’ve found a 1996 nickel which appears to be copper. Is it possible or did someone just deface it?
United States 5 cents pieces are struck on planchets consisting of 75% copper and 25% nickel. Most of the time the nickel has a silvery appearance as the coin’s color is dominated by the nickel metal. The nickel is very hard and does not corrode. In the presence of a strong oxidizer (acid, base etc) the nickel will take on a copper color. These coppery “nickels” are fairly common.
Errors do exist where a cent blank was struck with nickel dies (possibly a lone cent blank mixed up with nickel blanks). This error will have part of the outer design missing (since the planchet is too small), will be thinner than a standard nickel and will weigh less. These are easy to identify. Five cent coins weigh 5 grams, copper cents (pre 1982) weigh 3.11 grams.
Barring the error of a cent planchet being struck by a nickel die, the most likely explanation is the following:
The coin was struck from planchets from improperly mixed alloy. It is possible for the copper to come to the surface creating a coppery look to the nickel that eventually tones to a dark brown or black color. These do not bring a premium as they are of full weight and of the proper metal.